Display screen or portion thereof with a graphical user interface shown thereon



FIG. 1 is a front view of display screen or portion thereof with a graphical user interface shown thereon in an environment with a tablet;

FIG. 2 is a perspective view thereof;

FIG. 3 is a front view of display screen or portion thereof with a graphical user interface shown thereon in an environment with a monitor; and,

FIG. 4 is a perspective view thereof.

The broken lines showing the tablet in FIGS. 1 and 2 and the monitor in FIGS. 3 and 4 are included for the purpose of illustrating environmental structure; the broken lines showing portions of the graphical user interface and the display screen in all FIGS. are included for the purpose of illustrating portions of the article; all broken lines form no part of the claimed design. 

CLAIM The ornamental design for a display screen or portion thereof with a graphical user interface shown thereon, as shown and described. 